Carotenoids function in plants to absorb light energy for use in photosynthesis and also help to protect chlorophyll from degrading. Carotenoids are divided into two subclasses, carotenes (orange and red pigments) and xanthophylls (yellow pigments).
Animals are not able to synthesize carotenoids so they must obtain these compounds by eating plants and other organisms rich in carotenoids. Animals benefit from cartenoids in a number of ways. Carotenoids are responsible for coloration in many animals (notably birds and crustaceans) and this color is often used in courtship as a signal of health of the individual. Carotenoids are also believed to enhance vision and immune systems in some animals.